The IEC 62052-11 Ed.2 comes with a lot of changes for meter type testing. Another new introduced test for electromagnetic compatibility (EMC) is the ring wave immunity test.
The test method is described in IEC 61000-4-12. Here is only a brief overview for the required meter tests.
These tests verify the energy meter performance under the influence of power surges, coming from lightning or load switching at substations.
Firstly, you energize the voltage circuits with their highest specified nominal voltages. The connection cable length is defined with 1 m.
Then you read the active- and reactive SUM registers with high resolution. We need the readings later for the Pass/Fail evaluation.
All following tests have to be done with transients (our ring wave) at phase angles of 0°, 90°, 180° and 270°of the fundamental AC voltage waveform.
Five positive and five negative transients shall be applied at a rate of one transient per minute, at each specified phase angle.
So, the testing time for each of the following tests is 40 minutes. The tests are described for a direct connected three-phase four wire meter.
Test of the main meter terminals
a) You set the generator impedance to 12 Ω. Then you test between each line, including neutral, and ground with 4 kV. We take the mains-in terminals and have the disconnection relay closed. Total duration excluding wiring change is 160 minutes.
b) Now we are testing in differential mode each line to line and each line to neutral with 12 Ω and 2 kV. Means:
– L1 vs. L2
– L1 vs. L3
– L1 vs. N
– L2 vs. L3
– L2 vs. N
– L3 vs. N
As we are testing with both polarities, this set will cover all possibilities for our three-phase four wire meter. Total duration excluding wiring change is 240 minutes.
HLV signal ports
HLV means Hazardous Live Voltage. By IEC 62052- 31 these are voltages > 33 V RMS.
Auxiliary input- or output circuits are e.g. terminals for external relay control. Before doing the tests you need to be clear about the voltage terminal ratings.
The tests need to be done
a) between each line and ground with 12 Ω and 2 kV
b) in differential mode, line between line with 12 Ω and 1 kV
Potential-free contacts are tested in differential mode only.
ELV signal ports
ELV stands for Extra Low Voltage. These are terminals of auxiliary input or output circuits, data communication circuits and other auxiliary circuits rated for voltages < 33 V RMS.
The tests are done in common mode with 30 Ω and 0.5 kV. Common mode means, simultaneous coupling to all lines versus the ground.
We are building two signal groups:
a) all communication terminals are connected simultaneously
b) all signal ports are connected simultaneously
Total duration excluding wiring change is 80 minutes.
Acceptance criteria: B, the IEC wordings are in Italic
During the test, a temporary degradation or loss of primary functions is acceptable:
a) energy registration: at any time during the test, and immediately after, the value of energy registers shall not change by more than the critical change value;
At any time during the test is from my point of view not practicable. It’s sufficient to check the registers after all test are finished.
The Committee has also realized this and put a foot-note:
NOTE For tests of effects of external influence quantities or disturbances (9.3 and 9.4), constant monitoring of the indicating display during the whole duration of a test is not always feasible. In such cases it is sufficient to monitor the indicating display only when there is a reasonable doubt that the indicating display of the EUT may be susceptible to a particular influence quantity. The determination of such conditions is left to the expertise of the testing laboratory.
For evaluation, you read the SUM registers and compare the change versus the critical change value.
b) indicating display: degradation of display quality (colour, brightness, contrast, sharpness, geometry, etc.) during the test is acceptable; the indication of the content of energy registers may become unreadable during the test;
Nothing to do for evaluation.
c) supply and load control switches: unexpected operation of the switch during the test shall not occur.
You can either listen for several hours whether the relay makes the typical switching sound or your check the log-file for relay operation during your testing period.
During the test, a temporary degradation or loss of other meter functions within the scope of this document is acceptable, including a self-recovering reset of embedded software (firmware).
After the test when the disturbance is removed, and the reference test conditions are restored, the meter shall show no damage and shall operate with additional percentage error not exceeding the limits specified in the relevant particular requirements (accuracy class) standards.
That’s clear, I suggest doing the test with all items mentioned in the IEC 62058-31 for inspection.
All meter functions within the scope of this document shall be restored without any intervention of the operator, and without removal of the mains supply or the auxiliary power supply.
This means, you need to do the function tests at the ring wave generator station before you power down. Good that the IEC is stating this at the very end.
All meter functions within the scope of the IEC62052-11 Ed2. will take some time. I wonder what you are going to test?
Thank you for reading. As this test is newly introduced for energy meters, maybe we can have some mind exchange.
Editor's note: This article was originally published in August 2020 and has been updated for comprehensiveness.